According to U.S. Pat. No. 6,705,551 B1 (JP-A-2003-506622), as shown in FIG. 7, a fuel injection valve 100 has a fuel accumulator chamber 180 and a pressure control chamber 190 partitioned from each other by a cylinder 200. The fuel accumulator chamber 180 has a nozzle cavity 120 accommodating a valve element (needle) 140 adapted to opening and closing nozzle holes 130. The nozzle cavity 120 accumulates high-pressure fuel to be injected through the nozzle holes 130. The pressure control chamber 190 accumulates high-pressure fuel for controlling the opening and closing of the nozzle holes 130 using the needle 140.
The cylinder 200 of the fuel injection valve 100 is substantially in a cylindrical shape. The cylinder 200 has one end being in contact with a counter-nozzle hole wall surface 340 on the opposite side of the nozzle cavity 120. The needle 140 is slidably inserted in the inner circumferential periphery of the cylinder 200. In the present structure, the inner circumferential periphery of the cylinder 200 defines the pressure control chamber 190, and the outer wall of the cylinder 200 defines the fuel accumulator chamber 180. The movement of the needle 140 is controlled by manipulating pressure in the pressure control chamber 190, thereby intermittence of fuel injection from the nozzle holes 130 is controlled. The other end of the cylinder 200 has a spring seat 250 for supporting a spring 160. The spring 160 maintains the cylinder 200 in contact with the wall surface 340.
A fuel passage 310 opens in the wall surface 340 defining the nozzle cavity 120 for supplying high-pressure fuel to the fuel accumulator chamber 180. High-pressure fuel is supplied from the fuel passage 310 into the fuel accumulator chamber 180 every time when the needle 140 opens and closes the nozzle holes 130. The one end of the cylinder 200 is biased to the wall surface 340 by the spring 160 or the like. The cylinder 200 partitions the nozzle cavity 120 into the fuel accumulator chamber 180 and the pressure control chamber 190 by being biases from the spring 160. The area of the one end of the cylinder 200 is set small to enhance contact pressure relative to the wall surface 340. The other end of the cylinder 200 has the spring seat 250 for supporting the spring 160. The outer diameter of the one end of the cylinder 200 is less than the outer diameter of the other end of the cylinder 200. The inner diameter of the cylinder 200 is constant from the one end to the other end. The outer wall of the cylinder 200 has a step portion 230 in which the outer diameter of the cylinder 200 changes.
In the structure of U.S. Pat. No. 6,705,551 B1, as shown in FIG. 7, the step portion 230 is located immediately downstream of the wall surface 340 defining the nozzle cavity 120. Accordingly, when high-pressure fuel is supplied from through the fuel passage 310 opening on the wall surface 340, the flow of high-pressure fuel collides against the step portion 230 of the cylinder 200. Consequently, the cylinder 200 may move downward, and the cylinder 200 may be displaced away from the wall surface 340. When the cylinder 200 is moved away from the wall surface 340, the fuel accumulator chamber 180 communicates with the pressure control chamber 190. Consequently, pressure in the pressure control chamber 190 cannot be properly controlled. As a result, the needle 140 cannot be accuracy controlled to properly open and close the nozzle holes 130.